Electrostatic discharge (ESD) is a major issue for semiconductor circuits, particularly GaAs based circuits. A typical approach to providing ESD protection is to include diodes across the circuits to be protected. The diodes can be configured in either of forward or reverse biased configurations. In the forward biased configuration a number of diodes are connected in series to create a protection circuit with a trigger set by the barrier height of the diode multiplied by the number of diodes in the chain. This approach has the advantage that the trigger voltage can be scaled by the number of diodes in the chain. However, it has the disadvantage that the implementation can be large and require significant area on the integrated circuit. The typical turn on voltage for a diode is around 0.7 volts so creating a diode chain with a 14 volt trigger (for example) requires 20 diodes connected in series.
An alternative approach is to use a diode in reverse bias. In this case the trigger voltage is set by the diode's breakdown voltage which is typically 10-20 Volts. This is compact but is set by the intrinsic properties of the diode which are not easily altered.
The device according to the invention seeks to overcome the drawbacks of the prior art.